Problem: A computer sells for $\$900$ and loses $30\%$ of its value per year. Write a function that gives the computer's value, $V(t)$, $t$ years after it is sold. $V(t)=$
Explanation: Losing value at a rate of $30\%$ per year means the computer keeps $100\%-30\%=70\%$ of its value each year. So each year, the value is multiplied by $70\%$, which is the same as a factor of $0.7$. If we start with the initial value, $\$900$, and keep multiplying by $0.7$, this function gives us the value of the computer $t$ years from now: $V(t)=900(0.7)^t$